High-tension transformer



April 28, 1931.

H. B. SMETH HIGH TENSION TRANSFORMER Filed Aug. 14. 1929 4 Sheets-Sheetl 16 i Kg;

9 10 g I 9 10 i 11 12 25 INVENTOR Apri1 2 8, 1931. H, B, mm 1,802,678

HIGH TENS ION TRANSFORMER Filed Aug. 14, 1929 4 Sheets-Sheet 2 INVENTOR@5445 JMZPZ H. B. SMITH HIGH TENSION TRANSFORMER 4 Sheets-Sheet I 3April 28, 1931.

k Filed Aug. 14. 1929 April 28, 1931. a-a. B. SMITH HIGH TENSIONTRANSFORMER- Filed Aug. 14, 1929 4 Sheets-Sheet 4 Patented Apr. 28, 1931UNITED STATES PATENT OFFICE.

HAROLD B. SMITH, 0F WORCESTER, MASSACHUSETTS, ASSIGNOR TO WESTINGHOUSEELECTBIO & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIAHIGH-TENSION TRANSFORMER Application filed August 14, 1929. Serial No.885,943.

My invention relates to electrical translating devices, and it hasparticular relation to high-tension transformers.

It is the usual practice to immerse the windings and the associatedmagnetizable core structures of high-tension transformers in aninsulating fluid, such as oil, in order that the proper insulation maybe obtained between the windings and the core structures, and in orderthat the windings and core structures may be maintained comparativelycool.

Experience has demonstrated that a certain distance in oil ofa givenquality will insulate for a predetermined voltage, but that, as thevoltage is increased, the length of oil distance required increases at agreater rate. It is apparent that, as higher voltages are employed, therelative increase in space and volume required for oil is considerablygreater and, consequently, the size of the transformer assumes verylarge or even prohibitive proportions.

This difliculty has, to some extent, been overcome by employing platesor barriers of conducting material, and of annular form,

surrounding the high-tension winding and subdividing the oil space intoproperly divided sections. With this construction, the layers of thedielectric are each worked at potential gradients approaching theirdielectric strengths and suitable electrostatic densities, therebyincreasing the insulating value of the oil and decreasing the total oilspace and volume required.

It has been found that, at certain voltages and other conditions, acorona discharge occurs, under oil, in such apparatus, with the resultthat a certain amount of the insulating oil 'or other insulatingmaterial is decomposed, thereby causing the accumulation of deleterioussubstances which rapidly deteriorate the oil and other organic material.In addition to the decomposition of the insulating oil, there is anactualdeterioration of the other insulatingmaterial employed in thetransformer.

By removing all sharp edges from the several structural elements and byinterposing such suitable shieldsand flux distributors in the electricfields that the potential gradient between the several shields anddistributors shall not exceedcorona-forming or incipient ionizing orcorona values, the development of corona or incipient ionization orcoronaforming potentials are prevented.

It is usual to build up the high-tension winding with flat pancake orcylindrical coils. The difference of potentialbetween adjacent coils isdifferent at various parts of the coils, but the insulating spacebetween the coils has been great enough to take care of the maximumpotential difl'erence between the coils. Under these conditions, thedielectric is not 4 stressed uniformly and is not utilized to itsgreatest possible degree. It appears, with the present method of windingthat the dielectric is utilized to only about fifty percent of itsmaximum theoretical value. There is a' large and increasingly importantnumber of transformer applications where the currents are. relativelysmall and the voltages relatively high. If the cross section of copperappropriate to the relatively small current is used, the cross sectionof di-electric insulating space becomes of paramount importance.Inasmuch as the dimensions of a high-tension transformer depend, ingeneral, upon the dimensions of the space occupied by the high-tensionwinding, and the total volume, weight and cost depend upon that space.it is highly desirable to pro-- duce a transformer in which thehigh-tension winding shall be as compact as possible.

An object of my invention is to provide a transformer of theabove-indicated character that shall be simple, rugged, compact,easilymanufactured and adaptable for veryhighoil, usingelectric-flux-distributing shields for suppressing corona and incipientcorona and ionization, and so arranging the coils of. the high-tensionwindings, that the insu lating space between adjacent coils is built upin direct proportion to the increase in voltage, that I have been ableto greatly reduce the size, cost and weight of a transformer over thatheretofore obtainable.

For a better understanding of my inrention, reference is made to theaccompanying drawings, in which,

Figure 1 is a sectional elevational view of one embodiment of myinvention;

Fig. 2 is a perspective view, on a reduced v scale, of a metallicpotential-di'stributorv shield Fig. 3 is a sectional view of'a modifiedform of the upper turn of the high-tension winding;

' Fig. 4 is a view, partially in plan and pariially in section, of thetransformer shown in Fig. 5 is a sectional elevational viewof oneportion of the transformer windings;

Fig. 6 is a sectional view showing a portion of the high-tension windingemploying a metallic shieldbetween the adjacent coils;

Fig. 7 is a perspective view of a machine suitable for producing thecoils of the hightension winding, which is illustrated in Fig. 5,'and

Fig. of a coil and the manner in which it is sewed to a backing ofinsulating material.

Referring to Figs. 1, 4 and 5 of the drawings, my inventioncomprises,-in general, a

transformer 2 comprising a low-tension winding 3 and a high-tensionwinding 4 consisting of a plurality of coils 5 of flat conical formdisposed concentrically about 'a core member 6 in such manner that eachcoil makes a definite angle with adjacent coils.. The several coils areprovided, at their outer edges, with metallic potentialandflux-distributing members 7 of toroidal form. Nested metallic shields 8of annular form are attached to certain of the metallic distributors 7,for distributing the potential and Ilux fields generated within thetransformer. The shields 8 comprise cylindrical or annular portions 9and bottom portions 10 which are separate and have, respectively,toroidal portions 11 and 12 which are electrically connected to eachother when assembled. The distributing members 7, the annular portions 9and the bottom portions 10, inside and outside the high tension winding4, are split somewhere in their circumference, leaving an air gap 13, asillustrated in Fig.2, so as not to form short-circuited secondary turns.

The upper turn 14 of the high-tension winding consists of asemi-cylindrical tube composed of wood 15 and a sheet-metal outer cover16 having a split somewhere in its cir- 8 is a detail view showing aportion 0 cumference to avoid forming a short-circuited secondary turn.

The upper turn 14 of the high-tension winding may comprise, asillustrated in Fig. 3, a plurality of. turns of pipe formed into a'spiral that serves as a reactive inductance at the end of thehigh-tension winding to permit discharge of excess local potentialsbetween turns of the pipe through the insulating fluid medium. The uppercontour of the entire turn is curved so that, as in the case form, thatare disposed in nested relation and project upwardly concentrically withthe distributing terminal 17. The extensions 18 are severally connectedto horizontally extending portions 19 that terminate in toroidalpotential-and-flux-distributing members 20. The toroidal members 20 aredisposed concentrically about the distributingv terminal 17 insuch'manner that the potential gradient therefrom to ground or to eachother is maintained below corona or incipient corona or ionizingpotentials.

Concentric metallic shields 21 and 21a are provided above the winding 4to sub-divide the oil space and to complete the shield around eachsection of the winding. The shields 21 and 21a, respectively, areelectrically connected to corresponding cylinders 9 and thus have aspace 22 between them to prevent a short circuit of a section of thewlnding 4. The shields 21 and 21a are supported by insulating spacingmembers 23 disposed at certain points around the core 6. To allow the clindrical extensions 18 to extend upward y, the continuity of eachshield 21 and 21a is'necessarily interrupted, thus preventingtheformation of short-circuited secondary turns.

Tapered spacing blocks 24 and 25 are placed between the shields 9 andthe shield extensions 18. at certain points around the periphery to holdthem in spaced relation, the blocks associatedwith the left-hand portionof the shield being omitted for. clarity. Spacing blocks 26 are employedat certain points between the horizontally extending portions 19, theones to the left of the terminal 17 being omitted for clearness. Woodenor other dielectric supporting members .27 surround the core ,member andserve to support the v shields 8 and space them apart.

connected, by a suitable conductor 28, to

ground, thereby grounding that terminal of the high-tension winding 4.The uppermost fiat conical coil 5 is connected directly to the upperturn 14, and the latter is connected to. the distributing terminal 17,thereby placing the several coils 5 and the turn 14 in seriescircuitrelation between the terminals 17 and 28.

'The several coils 5 are formed of suitable very small wire on a backingof Fuller board 29 or the like,in a manner described heretube 7 are alltied matter. The coils are. maintained at a definite angle to each otherand at the angle at which they are wound and sewed by radial Wedge shapeinsulating members 30 which are inserted betweenthe coils at certainintervals. Disc members 31 of insulating material extend around the coremember between adjacent coils at the place of their greatest divergence;The disc members 31 are held in slots in the wedges and extendapproximately more than one-half the distance inwardly toward thejunction point of the adjacentcoils. The adjacent coils 5 are maintainedat such an angle that the space between corresponding turns of the coilsis great enough to insure with the discs and flux distributors su cientinsulating space between them. The disc members 31 may be employed toreduce the insulating space needed at the point of greatest potentialdifference, thereby reducing the size of the high-tension windmg.

At the end of the wedges 30, the two coils 5 on the Fuller board 29, thetwo pieces of Fuller board and the flux-distributing together by tapepassing through holes in the wedge and- Fuller board in a region at agiven potential and 0 without any difference of potential between thesepoints. This holds the radial wedge 30 in position without fastening atthe thick ends of the Wedge, where the maximum difference of potentialexists. It will be observed that every turn of each coil is exposed tofree circulation of oil, and the construction is such that any slightheating effect will facilitate such circulation and free the coils fromany small air bubbles or particles of moisture.

,Flat metal annular plates 32 split some where inthe circumference toprevent forming a short-circuited secondary, may be employed instead ofthe disc members 31. The annular plates 32 extend inwardly to thejunction point of the adjacent coils and are held bytwo triangular shapeinsulating members 33 that are substituted for the wedge-shape members31. At the junction point, the two coils 5, the two pieces of Fullerboard 29, the triangular shaped members 33 and the fluxdistributing tube7 are all connected together. The inner and outer edges of certain orall of the coils 5 are provided with toroidal distributors 7, in orderto distribute flux andpreventthe accumulation of coronaformingpotentials at the edges of the several coils 5. The distributor 7 may ormay not constitute the outer turn of the winding 5, as desired, and itmay also be omitted when possible.

Vith this construction, the insulating space is directly proportional tothe potential difference between coils at any point, and the dielectricis stressed with a close approach to absolute uniformity throughout thestack of coils 5 from terminal 17 to terminal 28. That is, I utilize theinsulating space to its maximum efliciency,thereby reducing to aminimum, the amount of high-tension-Winding space for a given quality ofdielectric at a predetermined high voltage.

Referring to Fig. 7 of the drawing, the apparatus for winding the coilscomprises a table 34 for holding the coil and the Winding equipment,although any suitable base may be employed, a motor-driven sewingmachine 35 that is adapted for zig-zag stitching, guide members 37. 38and 39 and spools of winding Wire 40 and insulating cord 41 suitablyattached to a leg of the table 34 by a support 42.

The guide'member 37 comprises two pulleys 43 and 44 rotatably mounted ona bolt 45 that is secured to the table 34. The guide member 38 comprisesan arm 46 suitably attached to a motor support 47 holding a roller 48.The guide member 39 comprises a plate 49 having a recess extendinglongitudinally therethrough of sufiicient size to accommodate the wire40 and the insulating cord 41.

on a pro ection 56 which extends upwardly from the table 34. A pluralitvof radial arms 56a extend outwardly from the center of the plate 55,holding two flat annular members 57 having the rim of an annular member58 of Fuller board, or similar material, disposed therebetween and heldtightly together by bolts 59 and nuts 60. A plurality of rollers 61 aredisposed under the Winding frame to facilitate the movement thereof. Theframe 54 is made of such size that the inside diameter of the Fullerboard is suitable for mounting in the transformer.

I the table to hold the edge of the uller board 58 up and prevent itfrom extending over Rollers 62 pro ect vertically u ward from mineddistance from the edge of the annular members 57. The winding wire 40and the insulating cord 41 are then fed, as indicated in Fig. 7 over thepulleys 43 and 44, respectively. under the roller/48 and the guidememher 39 and are sewed tothe Fuller board; As soon as the first turn ofthe wire and 1nsulating cord are sewed, the second turn of each is sewedto the first turn and to the moves away Fuller board, the ordinary feedmechanism of the sewing machine serving to rotate the disc andautomatically wind the spiral.

Sometimes it may be necessary to provlde an auxiliary drive for thedisc. For this purpose, I have provided a motor 64, mounted on a bracket65 attached to a leg of the table 34. A belt 66, passing over thepulleys 67, located in the table, serves to connect the pulley of themotor-64 and the center plate 55. Insewing the wire and the insulatingcord to the Fuller board, the thread passes over several turns of each,extends through the insulating cord, loops through the Fuller board andpasses over several more turns in zig-zag shape, substantially as shownfor an insulated conductor in Fig. 8. Astbe sewing process is continued,the sewing needle from the center of the coil 'to adjust itself to theincreasing diameter of the coil. When the coil is completed, the flatannular members 57 are taken, apart and the coil removed. The portion ofthe frame '54, except the Fuller board, may be used again in windingother coils.

When it is desired to make the coil of insulated conductor, theinsulating cord 41 'is omitted and, in stitching, the thread passes overseveral turns of the insulated conductor, extends through theinsulation, loops through the'Fuller board and passes over several moreturns of the coil, similarly to the operation hereinbefore described.

The axis of the frame 38 may be placed at any angle with the sewingmachine that is desired by change inthe angle of the winding table ormachine or both. This permits the production of a coil of a single layerwith any angle desired for the conical surface of the coil, from flatpancake coils illustrated in this embodiment to fully cylindrical coils.The important angles for such conical windings are those approaching theplane flat coil illustrated herein, or those angles approaching acylinder, either of which may be wound on this machine.

From the foregoing description, it will be apparent that I have provideda high-tension transformer in which the space required for thehigh-tension winding is materially reduced, thereby makingthetransformer more compact andeconomica-l.

The accompanying descriptionand illustration are merely illustrative andare not to be construed in a limiting sense. Since many modifications,within the spirit and scope of my invention, may occur to those skilledin the art, I do not wish to be limited otherwise than by the scope ofthe appended claims.

I claim as my invention:

1. In a transformer, a magnetizable core member, a plurality of windingssurrounding said core member and submerged in an insulating fluid, oneof said windings com prising a plurality of coils, each coil disposed atan angle to the adjacent 0011 so that the dielectric between said coilsis stressed uniformly, a potential-control and flux-distributing meansof annular form attached to each pair of, coils atthe point ofzero-potential difl'erence between the coils, and potential-control andflux distributing shields electrically associated with certain of saidannular dissulating barrier disposed between adjacent coils at the pointof greatest divergence and extending toward the apex of the two coilsfor a certain distance, the end coil having a contour, the generalradius of curvature ofwhich is such that the potential gradient at ornear its surface is less than will causeincipient corona or ionization,said end coil comprising a helix of tubular conducting material.

3. A high-potential winding, comprising a plurality of circular coilsdisposed in vertical alinement and at such an angle to each other thatthe dielectric stress between adjacent coils is substantially uniform,an insulating barrier disposed between adjacent coils at the point ofwidest separationand extending inwardly toward the apex of the twoadjacent coils, radial wedges disposed at certain points aI'OllIkd thecoil for maintains ing the coils at the desired angle, the end turnhaving a contour, the radius of curvature bf which is such that thepotential gradient at or near its surface is less than will causeincipient corona or ionization.

4. A coil for electrical apparatus comprising a series of convolutionsof insulated wire disposed in a single plane, the successiveconvolutions of the insulating covering being sewed to each other and toa backing member of insulating material by zig-zag stitches constitutinga spiral.

5. A coil for electrical apparatus comprising a series of convolutionsof insulated wire disposed in a single plane, the successiveconvolutions of the insulating covering being sewed to each other and toa backing member of insulating material by zig-zag stitches constitutinga spiral.

6. A coil for electrical apparatus comprising a series of convolutionsof insulated wire forming a conical surface, the successive convolutionsbeing sewed to each other and to a backing member of insulating materialby zig-zag stitches and constituting a conical spiral.

7. A. coil comprising a spiral of smallgauge insulated wire, thesuccessive turns of the insulation being sewed to each other and to aninsulating backing member by zig-zag stitches constituting a spiral.

8. The method of forming a coil for electrical apparatus which consistsin attaching one turn of said coil to a base and attaching eachsuccessive turn to the turn or turns next preceding it and to the baseby zig-zag stitches.

9. The method of forming a coil for electrical apparatus having aplurality of convolutions of insulated wire, said convolutions beingdisposed on a base at any desired angle to the axis of the coil, whichconsists in placing the axis of a form carrying the base at the desiredangle with respect to a sewing surface, sewing one turn to the base andsewing each successive turn to the turns preceding it and to the base byzigzag stitches 1 0. The method of forming a coil for elec tric alapparatus having the convolutions of said coil disposed at any desiredangle to the axis oi the coil which consists in placing the axis of aform carrying a base for the coil the desired angleto a sewing surface,sewing one turn to the base, gradually rotating the base, stitching eachsucceeding turn or turns to the next preceding turn or turns and to thebase and adjusting the stitching point to accommodate the increase indiameter of the coil.

11.. A. coil for electrical apparatus comprising aseries of alternateconvolutions of wire prising a series of alternate convolutions of wireand insulating material forming a conical surface, the successiveconvolutions being sewed to each other and to a backing member ofinsulating material by zig-zag stitches and constituting a spiral.

13. A coil for electrical apparatus comprising a series of alternateconvolutions of bare wire and insulating material forming a conicalsurface, the successive convolutions being sewed to each other and to abacking member of insulating material by zig-zag stitches andconstituting a spiral.

14. The method of forming a coil for electrical apparatus having aplurality of alternate convolutions elf-conductor and insulatingmaterial, the said convolutions being disposed at any desired angle tothe axis of the coil, which consists in placing the axis of a formcarrying a base for the coil at any desired angle to a sewing surface,gradually rotating the form and stitching the alternate convolutions ofconductor and insulating material to the base and to each other byzigzag stitches, and adjusting the stitching point to accommodate theincrease in diameter or the coil.

In testimony whereof, I have hereunto subscribed my name this ?th day ofAugust,

HABULD B. SMITH.

and insulating material disposed in a single Q plane, the successiveconvolutions being sewed to each other and to a background of insulatingmaterialby zig-zag stitches constitutmg a spiral.

12. A. coil for electrical apparatus com-

